In addition to shape, the Postal Service classifies mailpieces by the way they are prepared. These classifications are based on how efficiently your mailpieces can be processed on Postal Service equipment. The Postal Service classifies commercial flats as either nonautomation or automation flats or machinable and nonmachinable for Periodicals.

A flat meets automation standards and qualifies for automation prices if it meets the specific addressing, barcoding, and design standards. Automation flats must have a POSTNET or Intelligent Mail barcode with a delivery point routing code.

Uniform thickness: the contents must be uniformly thick so that any bumps, protrusions, or irregularities do not cause more than 1/4 inch variance in thickness (301.1.4). When determining variance in thickness, exclude the outer edges of a mailpiece (1 inch from each edge) when the contents do not extend to the edges.

Mailpieces that do not meet the standards for flexibility in 301.1.3, or for uniform thickness in 301.1.4, must pay applicable prices as follows: